(a) Field of the Invention
The present invention relates to a thermo-developable type diazo copying material, in particular relates to a fixable diazo system heat-sensitive recording material.
(b) Description of the Prior Art
Thermo-developable type diazo copying materials are well known wherein the reaction of a diazo compound with a coupler is designed to be effected by heating. However, any one of the conventional thermo-developable type diazo copying materials, when viewed from the practical aspect, is not satisfactory in the points of raw preservability (preservability of the copying materials per se before use) and thermo-color formability.
Due to this, in the preparation of thermo-developable type diazo copying materials there have been proposed for instance (1) to isolate active components (diazo compound and coupler) by an intermediate layer as disclosed in British Pat. No. 815005 and to pulverize one of the active components into fine particles and encapsulate said fine particles with a continuous, non-permeable shell as disclosed in U.S. Pat. No. 3,111,407, and (2) to add, as color assistants, heat-fusible substances such as paraffin and the like having a melting point of 45.degree.-150.degree. C. as disclosed in Japanese Patent Publication No. 839/1969 for the purpose of obtaining the products of high color formability. However, the above mentioned method (1) is defective in that the heat sensitivity is apt to deteriorate, and the above mentioned method (2) is defective in that the raw preservability deteriorates. As seen from the aforegoing, the fact is that it is impossible at the present time to find thermo-developable type diazo copying materials which can satisfy the requirements of raw preservability and heat sensitivity (low temperature development) at the same time.